实现功能
- 读取用户throttling配置，对broker的连接、消息进行限制，以保证broker在最健康、最效率的时间去serve
类图
这里写图片描述
- 它的流量限制是使用GlobalTrafficShapingHandler去完成的，由GlobalTrafficShapingHandlerProvider来提供。
public class GlobalTrafficShapingHandlerProvider
implements Provider<GlobalTrafficShapingHandler> {
private static final Logger LOGGER = LoggerFactory.getLogger(GlobalTrafficShapingHandlerProvider.class);
private final ShutdownRegistry shutdownRegistry;
private final ThrottlingConfigurationService throttlingConfigurationService;
@Inject
GlobalTrafficShapingHandlerProvider(ShutdownRegistry shutdownRegistry,
ThrottlingConfigurationService throttlingConfigurationService) {
this.shutdownRegistry = shutdownRegistry;
this.throttlingConfigurationService = throttlingConfigurationService;
}
@Override
public GlobalTrafficShapingHandler get() {
ThreadFactory threadFactory = new ThreadFactoryBuilder().setNameFormat("global-traffic-shaping-executor-%d").build();
ScheduledExecutorService globalTrafficShapingExecutorService = Executors.newSingleThreadScheduledExecutor(threadFactory);
GlobalTrafficShapingExecutorShutdown shutdown = new GlobalTrafficShapingExecutorShutdown(globalTrafficShapingExecutorService);
this.shutdownRegistry.register(shutdown);
long incomingLimit = this.throttlingConfigurationService.incomingLimit();
LOGGER.debug("Throttling incoming traffic to {} B/s", incomingLimit);
long outgoingLimit = this.throttlingConfigurationService.outgoingLimit();
LOGGER.debug("Throttling outgoing traffic to {} B/s", outgoingLimit);
GlobalTrafficShapingHandler handler = new GlobalTrafficShapingHandler(globalTrafficShapingExecutorService, outgoingLimit, incomingLimit, 1000L);
ValueChangedCallback changedCallback = createValueChangedCallback(handler);
this.throttlingConfigurationService.incomingLimitChanged(changedCallback);
this.throttlingConfigurationService.outgoingLimitChanged(changedCallback);
return handler;
}
@NotNull
private ValueChangedCallback<Long> createValueChangedCallback(GlobalTrafficShapingHandler handler) {
return new ThrottlingTrafficLimitValueChangedCallback(handler, this.throttlingConfigurationService);
}
private static class ThrottlingTrafficLimitValueChangedCallback
implements ValueChangedCallback<Long> {
private final GlobalTrafficShapingHandler globalTrafficShapingHandler;
private final ThrottlingConfigurationService throttlingConfigurationService;
public ThrottlingTrafficLimitValueChangedCallback(GlobalTrafficShapingHandler globalTrafficShapingHandler,
ThrottlingConfigurationService throttlingConfigurationService) {
this.globalTrafficShapingHandler = globalTrafficShapingHandler;
this.throttlingConfigurationService = throttlingConfigurationService;
}
@Override
public void valueChanged(Long newValue) {
this.globalTrafficShapingHandler.configure(
this.throttlingConfigurationService.outgoingLimit(),
this.throttlingConfigurationService.incomingLimit());
}
}
}
GlobalTrafficShapingHandlerProvider通过使用ThrottlingConfigurationService读取用户配置，来限制incoming和outgoing。
同时给ShutdownRegistry注册一个GlobalTrafficShapingExecutorShutdown，以当broker关闭时，能够关闭GlobalTrafficShapingHandler中的ScheduledExecutorService。
由于MQTT协议中对remainingLength的限制在256m，如此大的数据，如果发到服务端，如果数量再一多，再优秀的mqtt broker都扛不住，所以它还提供了自定义最大消息长度，以保证broker稳定运行，以及攻击，是一个阻拦。 在MqttMessageDecoder中，来判断最大消息长度，来限制连接。
LicenseConnectionLimiter是它读取license之后，根据license限制做的一个连接数限制，以及连接数占最大连接数限制的报警百分比限制。具体的license读取、license验证、license加密这一块由于不属于本章内容，所以不做过多细节介绍，并且由于它是商用软件，所以细节以后也不会不做透漏，请各位朋友谅解；因为本系列只是协助大家了解企业级的broker如何实现的，它考虑的思路是什么，而不是破坏别人知识产权的。
